It affiliated to the Irish Trades Union Congress in 1931, finally overcoming the opposition of the ASW.
In 1942, it was prominent in the formation of the Building Workers' Trade Union (BWTU), to which it affiliated.
During this period, it was affiliated to the Irish Congress of Trade Unions.
In 1971, it was a founding affiliate of the new Federation of Irish Industrial and Building Operatives' Trade Union, a loose federation which collapsed after a couple of years.
The union's membership grew steadily over the years, reaching a peak of 2,000 in 1979.